Method for forming shapes from sheet metal



May 24, 1938. M. c. DURBIN 2,118,499

METHOD FOR FORMING SHAPES FROM SHEET METAL Filed Dec. 10, 1936 INVENTOR.

Patented May 24, 1938 UNITED STATES METHOD FOR FORMING SHAPES FROM SHEET METAL Malcolm C. ,Durbin, Jamaica, N. Y.

Application December 10, 1936, Serial No. 115,130

2 Claims.

This invention relates to a method for forming shapes from sheet metal and a particular object of the invention is to form shapes from sheet stock that has square corners and a further object of the invention is to form shapes from sheet stock by displacing the metal at the corners so as to provide a groove at the inside of the bend in the stock and to provide outside corners that may be trimmed off square with the surface of the sheet stock. Other objects of the invention will be more particularly understood from the following specification and from the accompanying drawing, in which- Fig. 1 is an end view of sheet stock formed in 5 a channel in which part of the process of this invention has been used;

Fig. 2 is a cross section of a channel shape formed according to this invention and used as a cover or shield for a. channel iron;

Fig. 3 is an end View of a shape such as is commonly used on door jambs constructed according to this invention;

Fig. 4 is an end view of a rectangular form of tube made according to this invention;

Fig. 5 is an elevation of a pair of dies used to form the corners of the sheet stock which is shown in section in the dies, and

Fig. 6 is, a form of abrasive belt that may be used to trim the corners after the bending operation when square corners are desired.

In architectural and ornamental work it is common practice to provide a veneer of sheet metal, such as brass, bronze or aluminum on doors, windows and the like and for this purpose the trade has provided a variety of shapes which are made by extruding dies, or by a drawing process and in each case special dies are required for each shape, the stock has to be manufactured in quantities and stored, and in general the cost of the shapes is comparatively high.

The structural steel shapes are produced according to standard sizes by the rolling mills but light angles and channels are now generally produced from sheet stock in a break. This process enables the shapes to be formed from sheet stock as required and without the application of heat.

Shapes formed on a break from sheet stock always have round corners as the stock is bent around a, mandrel and the thickness or cross section of the stock at the corners is the same as in the body. For many purposes, particularly of an ornamental character, square corners are required on the shapes which cannot be produced in the ordinary process by a break with the result that shapes of this type have to be extruded or (Cl. 1l3-116) produced by some of the more expensive methods. It is the purpose of this invention to provide a break equipped with a die that will displace the stock at the corner from the inside towards the outside of the bend providing protrusions on the outside at the corners that provides a fillet at the outer apex of the bend sufficient to provide a square corner when the protrusions are ground away flush with the surface of the stock. In addition to this a groove is provided on the inside of the corners instead of the usual curved fillet so that shapes bent in this way can be applied to other members having a, sharpe edge.

In addition to providing stock formed into shapes with square corners, the working or drawing operation of the dies on the corners of nonferrous metals hardens the metal at this point with the result that a comparatively rigid construction, capable of resisting ordinary shocks at the corners, is obtained in shapes formed according to this process.

Shapes with square corners can be formed into frames for doors and the like and where the shapes meet the edges are flush and the seam can be concealed. While the process herein disclosed is particularly adaptable for non-ferrous metals, it may also be used for sheet steel constructions.

In the drawing, II indicates a strip of sheet stock which is bent upwards at the sides as indicated at I! and I3 to form a channel. The inner corners are provided with grooves shown at M and I5 and the outer corners, as indicated in Fig. 1, have rounded protrusions indicated at I6, which extend below the surface I! of the sheet stock.

A channel made in this form can be applied to a structural steel channel l9, Fig. 2, without trimming the corners of the steel channel. This is due to the fact that the grooves l4 and I5 provide a clearance for the sharp corners of the channel l9, making a snug fit between the cover ing channel I1 and the structural channel I9. In Fig. 2 the outer channel has the corners trimmed off flush at IS with the outer surfaces of the stock I2, l3 and [1, thereby making square or right angle corners.

The shape in Fig. 3 is designed for a door jam which may be provided with the supporting member 20. This shape, 2|, has a central extension 23 and is provided with sides as indicated at 22. It will be observed that the outer corners 24 are trimmed off square, making a sharp edge and that the inner corners oi. the bends indicated by 25 are formed in a groove corresponding to the grooves II and I5, Fig. 1.

The shapes may-be made in a variety of forms, the usual plan is to form one bend at a time with the groove in the corner and afterwards to progress by subsequent bends oi push out type described herein; all bends do not have to be of this type as at times it is desirable in certain shapes to have one or more 01 the usual break (round corner bends) in the sequence. This arrangement has been followed in forming the rectangular tube, Fig. 4, in which the tube is iormed from a single piece 0! sheet stock having the sides 26 and 21, the bottom 28 and the wings I! and 30, at the top. Each corner is formed with the groove I2 on the inner side 01' the bend and when the shape is finished the outer corners are trimmed oil square as indicated at ii. The last operation in forming this shape is indicated by the dotted lines in which the sides 26' and 21' are brought into position by straightening out the curved bottom member 28 with the usual flattening die.

One form of die that may be used in practicing this invention is illustrated in Fig. 5 in which the upper die member ii of the break registers with the lower die member 2 and engages the stock H between these members, subject to the pressure of the machine. The lower member is iormed with a curved pocket 53 which is opposed by the curved spud 54 of the top die. The pressure on the top die not only bends the stock II and 12 into a right angle, but it forms a groove corresponding to II on the inner side of the bend and it displaces the metal of the stock into the protrusions 58-55. The dotted lines indicate the plane 0! the outer surfaces II and I! which meet at their apex within the protrusions so that as the protrusions are ground away flush with the surfaces II and ii, a sharp corner is provided at the apex, which is indicated in Fig. 5 on an enlarged scale.

The construction in Fig. 6 is a diagram of a belt-type grinder that may be used to trim the protrusions on the outside of the corners. This comprises the belt wheel 88, mounted on the shaft 59, and the companion belt wheel mounted on shaft 6|, with the abrasive belt 62 mounted on these wheels and suitably driven by means not shown in the drawing. The belt passes over the channel i I and is held in alignment by the guide 64. Under these conditions the belt grinds away the protrusions 55 on the edges of the channel until the bottom of the channel is level. The operation is then repeated with reference to the sides I 2 and I3, thereby removing the surplus material at the corners and leaving a square edge. When brass or other non-ferrous metals are used the corners SI that are worked by the die are thereby hardened and the lasting qualities oi! the shape are increased.

Having thus described my invention, I claim:

1. A method of forming shapes having a plurality of square corners from sheet metal comprising bending the stock at each corner in a die arranged to displace the metal from the inside of the corner to form protrusions on the outside of the corners, grinding away the protrusions to form the square corners and bending the stock to the final shape desired.

2. A method of forming a rectangular shape having a plurality of square corners from sheet metal comprising bending the stock at each corner in a die arranged to displace the metal on the outside of the corner so that the stock will fill the apex of the square corner to excess on the outside, bending the stock to shape, and grinding away the excess stock to align with the adjacent sides.

MALCOLM C. DURBIN. 

